Safe Pediatric Trial of Euglycemia in Cardiac Surgery (SPECS) Critically ill neonates and children commonly develop stress hyperglycemia which is significantly associated with increased morbidity and mortality. In critically ill adults several clinical trials have found that tight glycemic control with intravenous insulin therapy decreases morbidity and mortality, primarily through decreased incidence of sepsis. The recent development and validation of continuous glucose monitoring now allows safe administration of insulin to critically ill children with minimized risk of severe hypoglycemia. The proposed study seeks to test the hypothesis that the application of safe tight glycemic control with insulin infusion will result in improved post-operative outcomes in pediatric cardiac surgery patients. To date, there have been no pediatric randomized trials of tight glycemic control. The results of this study will provide much needed evidence for treatment of hyperglycemia in post-operative critically ill pediatric patients and advance the understanding of the impact of metabolic factors on post-operative recovery. A single-center prospective randomized controlled trial is proposed employing continuous glucose monitoring and insulin infusion to maintain euglycemia in post-operative pediatric cardiac surgery patients less than three years of age. The protocol is designed to determine if the application of tight glycemic control will result in a decreased rate of nosocomial infection, and to examine the effect of euglycemia on organ system recovery and function. This innovative investigation has the potential to lead to improved management and decreased post- operative morbidity in neonates, infants, and children with congenital cardiac defects and is important in defining the need for tight glycemic control in all pediatric critically ill patients. Critically ill children commonly develop elevated blood sugars during their illness which has been demonstrated to be associated with poorer outcome. Adult studies have shown that strict maintenance of the blood sugar in the normal range reduces mortality and improves outcome, but this has never been tested in children due to the safety issues around insulin infusion and possible low blood sugars. This study will test the value of strict control of the blood sugar in critically ill children after open heart surgery using newly available and validated continuous blood sugar monitoring to detect and prevent low blood sugars, and to allow for safe maintenance of the blood sugar within the normal range.